Articulated ladder construction for cutterhead dredge

ABSTRACT

An articulated ladder for a cutterhead dredge especially adapted for use in rough water and wherein the ladder, rather than being a unitary rigid member, is constructed in two parts connected together at adjacent ends by a link whereby the thrust due to wave action on the ladder part trunnioned to the dredge cannot be transmitted to the cutterhead and, by reaction of the latter against the bottom, back to the trunnions.

waited States Patent Turner et al.

ARTICULATED LADDER CONSTRUCTION FOR CUTTERHEAD DREDGE Inventors: Thomas M. Turner, Severna Park; Francis J. Keefe; Charles D. Little, both of Baltimore, all of Md.

Ellicott Machine Corporation, Baltimore, Md.

Filed: Feb. 4, 1972 Appl. No.: 223,482

Assignee:

U.S. Cl. 37/67, 37/72 Int. Cl E02t 3/90 Field of Search 37/58, 64-67, 37/72 References Cited UNITED STATES PATENTS 5/1971 Jantzen 37/72 X Dec. 11., 1973 8/1972 DeKoning et al 37/72 X Primary Examiner-Robert E. Pulfrey Assistant Examiner-Clifford D. Crowder AttorneySamuel Scrivener, Jr. et al.

[57] ABSTRACT An articulated ladder for a cutterhead dredge especially adapted for use in rough water and wherein the 9 Claims, 3 Drawing Figures Riedemann 37/67 UX ,PATENIEUnEc 1 I ma TBSF 3 NEE ARTICULATED LADDER CONSTRUCTION FOR CUTTERHEAD DREDGE This invention relates to dredges and more particularly to cutterhead dredges especially adapted to working in heavy seas.

Erosion of ocean beaches in recent years has been unusually severe and the only practical way to restore beach areas lost through erosion is to pump back onto the beaches sand from adjacent waterways. In some regions sand is available in bays which separate so-called sea islands from the mainland and where sufficient sand is available from this source the dredging apparatus does not have to contend with the problem of rolling and pitching action as would be the case were the dredge to operate in the open ocean.

Where the sand in bays is insufficient or there are no bays, then the most readily available supply of sand is from the ocean floor adjacentthe beach. He retofore, however, dredging in the open ocean by cutterhead dredges has been uneconomical because of the inability of the dredge to operate in the ocean except on calm days. In the usual cutterhead dredge the cutterhead is mounted at the end of the unitary, rigid ladder trunnioned at its upper end directly to the hull and when the hull pitches downwardly due to wave action, the ladder drives the cutterhead against the bottom and transmits back to the trunnion a tremendous shock load'capable of seriously damaging the ladder, trunnions, etc. To avoid this, cutterhead dredges operating in the open sea suspend operations under even relatively mild sea conditions and the object of the present invention is to provide a cutterhead dredge which is so constructed that it is capable of operating over a much wider range of sea conditions that has been possible heretofore with conventional cutterhead dredges.

More particularly it is an object-of the invention to provide a cutterhead dredge wherein the ladder, rather than being a rigid unitary member as heretofore, is articulated with upper and lower sections being connected together by a link which enables the upper section trunnioned to the hull to move with the hull in a sea without transmitting thrust to the lower section and its cutterhead.

Other objects and-their attendant advantages will become apparent as the following detaileddescription is read in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevational view of the front end of a dredge showing the present invention with a part of the control system being shown schematically;

FIG. 2 is an enlarged side elevational view of a ladder constructed in accordance with the invention; and

FIG. 3 is a front elevational view of the ladder of FIG. 2.

Referring now to the drawings, the numeral designates a dredgehull carrying the usual control cabin or pilot house 11 and whose front end is bifurcated in the usual way at 12 (see FIG. 3) to pivotally receive on trunnions 14 the upper end of a dredge ladder broadly designated by the numeral 16.

As can be clearly seen, the ladder 16 rather than being a unitary rigid member is constructed in two upper and lower parts 18, with the inner end of the part 18 being received on the trunnions 14 while the outer end of the other part 20 carries a rotary cutterhead 22 which is connected by a shaft 23 to a hydraulic motor or motors 24 receiving operating fluid from the hull by way of flexible conduits 26.

In accordance with the invention, the outer and inner ends of the respective parts 18, 20 of the ladder are freely pivotally connected to the opposite ends of a link 28 which, as can be seen in FIG. 3, is somewhat H- shaped in configuration with the upper arms 30 being bifurcated to receive laterally spaced forwardly extending projections 32 at the outer end of the ladder part 18. Extending through registering openings in the parts 30 of the link 28 and the parts 32 of the ladder part 18 are bearing pins 34, 36 whereby the upper end of link 28 is freely pivoted to and swingably depends from the outer end of the ladder part 18.

In like manner the inner end of the outer ladder part 20 is pivoted on pins 38, 40 to the lower arms 42 of the link member 28. The outer ladder part 20 carriesa centrifugal pump 46 driven by a hydraulic motor or motors 48 receiving hydraulic operating fluid from the hull via flexible conduits 50 as shown. The inlet of the pump 46 is connected by a suction pipe 52 to the interior of the cutterhead 22 in the usual manner and the outlet of the pump leads to a passage through the lower pivot pin 38 which is connected by a conventional swivel coupling 54 to a lower end of a pipe section 56 whose upper end is connected by a similar swivel coupling 58 to a passageway through the upper pivot pin' 34 leading to a suction line 59 carried by the upper ladder part and leading to the inlet of a second centrifugal pump 60 (see FIG. 1) whose outlet may be connected to a pipe line 61 leading to the beach.

Fixed to the upper side of the lower ladder part 20 are a pair of laterally spaced brackets 62 and fixed to the lower end of the upper ladderpart 18 are a second pair of brackets 63. Connected to each bracket 63 is the upper end of a hydraulic cylinder 64 containing a piston 66 whose plunger 68 is connected to one of the brackets 62 on the lower ladder part. As can be seen, the cylinder 64 has an inlet port 68 below the piston 66 and which, as schematically shown in FIG. 1, is connected by a conduit 70 to the hydraulic side of a combined air pressure-hydraulic cylinder or accumulator 72 in the hull. The accumulator is equipped with the usual piston or diaphragm 74 separating the hydraulic cavity 76 from the pneumatic pressure cavity 78 and the latter is connected to a pressure reservoir 80 by a conduit 82 containing a manually operated pressure regulating valve 84 conveniently located in the pilot house 11 of the hull for ready adjustment by the dredge operator, the reservoir 80 being supplied with pressure from a compressor 86. Though only one accumulator 72 is shown preferably one or more accumulators is connected to each of the hydraulic cylinders 64. The purpose and manner of operation of the hydraulic cylinders and pistons 64, 66 will become apparent hereinafter.

The ladder is moved between its working and nonworking positions by a winch 86 carrying a cable 87 trained around sets of sheaves 88, 90 carried on scaffolding structure 92 at the front end of the hull and on the outer end of the ladder part 18, respectively. The scaffolding structure may extend forwardly of the hull and carry the usual restraining devices (not shown) for supporting the ladder when in its raised, transport position. The ladder part 18 also carries the usual sheaves Y 94 around which cables 96 leading from winches 98 are trained for connection to the usual anchors for controlling the lateral movement of the cutter-head, ladder, etc. in the conventional fashion during dredging operations.

In operation, the hull is towed to its place of operation, the spuds or stern mooring anchors are lowered, and the anchors set out in the customary manner. The inner ladder part 18 is then lowered to its working position having regard to the state of the sea so that the lower end of the link is sufficiently spaced above the bottom 100 that when the bow of the barge pitches downwardly the link at all times remains clear of the bottom. It will be apparent that should the link strike the sea bottom during a downward pitch of the hull, a shock of significant magnitude might be transmitted to the ladder trunnions l4 and the prime purpose of the present invention is to provide such action.

While the main or inner ladder part 18 is being psoitioned in working condition, sufficiently high pressure is delivered to the accumulator so that the piston 66 in the hydraulic cylinder is retained in a retracted position so as to substantially lock the lower ladder part in a raised position relative to the link 28. After the upper ladder part has been properly positioned, the operator} then relieves the pneumatic pressure in the accumulator to a predetermined level by manipulation of the valve 84 until the weight of the lower ladder part moves the piston 66 in opposition to the hydraulic pressure acting on the piston 66. The operator never intentionally releases all of the pneumatic pressure from the accumulator but rather sets the valve 84 so that the accumulator pressure is retained at a sufficient level whereby the lower ladder part is partially supported and the cutterhead engages the bottom with a substantially constant predetermined force regardless of the rise and fall of the forward end of the hull in seas.

As an example of the foregoing, let it be assumed that if there were no support at all for the lower ladder part, the cutterhead would rest directly on the bottom with a weight of 100,000 pounds. Now let it be assumed that sufficient pneumatic pressure is admitted to the accumulator to produce a hydraulic pressure acting on the piston 66 so that it exerts a lifting force of 50,000 pounds on the lower ladder part whereby the cutterhead now engages the bottom with a net downward force of 50,000 pounds, which is assumed to be the desired force for efficient dredging operations considering the state of the bottom. Now it will be seen that should the hull bow rise due to wave action, the weight of the lower ladder part pulls the piston downwardly against the opposing hydraulic pressure causing the piston 74 in the accumulator to rise and further compress the air in the cavity 78. However, the accumulators are sized such that the pneumatic pressure change is limited to a predetermined value so that the pneumatic pressure acting on the piston 74 and the consequent lifting force of the hydraulic pressure acting on the piston 66 remains relatively constant so that the cutterhead and the lower ladder part, due to their weights, cause the head to exert a net downward force on the bottom of approximately 50,000 pounds. Under the reverse conditions, when the bow of the hull descends, the cutterhead is increasingly supported by the bottom so that the downward force opposing the hydraulic pressure in the cylinder is decreased. Simultaneously, the preset pneumatic pressure in the accumulator forces the accumulator pistons 74 downwardly so that hydraulic pressure operating on the piston 66 continues to exert a lifting force on the lower ladder part 20 of approximately 50,000 pounds.

After the cutterhead has been disposed in working position, the operator energizes the hydraulic motors 24 and 48 to operate the cutterhead and the laddercarried hydraulic pump 46 and at the same time the the upperm energizes the upper, barge-carried pump 60.

From the foregoing description, it should be apparent that as the front end of the hull pitches in seas, instead of a shock being transmitted directly to the trunnions due to the cutterhead being driven into the bottom as would occur were the ladder rigid, with the present invention, as the front end of the hull descends the upper ladder part descends with it with no change in the angularity of the ladder part relative to the axis of the hull. However, any downward thrust of the upper ladder part 18 is now exerted against the upper end of the link 28, which merely pivots or swings relative to the ladder part 18 while the opposite end of the link pivots relative to the end of the lower ladder part 20 so that substantially none or only an insignificant portion of the thrust of the upper ladder part 18 can be transmitted to the cutterhead and back to the trunnions.

If the sea is especially rough the dredge might not be able to operate because of the danger of the link engaging the bottom. Under thesecircumstances, dredging operations would be suspended but except under unusually rough conditions, dredging operations may continue over a wide range of sea conditions unacceptable for standard dredging apparatus. It has been determined that a ladder constructed in accordance with the present invention can operate in various oceans over approximately of any given period of time. whereas a conventional cutterhead dredge can only operate a small fraction of time for the same given period.

It will be apparent that the invention is susceptible of changes and modifications without, however, departing from the scope and spirit of the appended claims.

What is claimed is:

1. Dredging apparatus for use in heavy seas comprising a barge and an articulated ladder, said ladder comprising a first rigid upper ladder part having its inner end pivoted to said barge, a second rigid lower ladder part carrying adjacent its outer end a cutterhead, a downwardly extending rigid link having its upper end freely pivoted to the outer end of said first ladder part so that said link swingably depends from said outer end, said link having its lower end freely pivoted to the inner end of the second ladder part so that said second ladder part is angularly movable relative to the upper ladder part, and means for adjustably positioning said first ladder part at a selected angle relative to said barge so that the lower end of said link is positioned clear above the sea bottom during dredging operations in heavy seas.

2. Apparatus of claim 1 including means carried by said second ladder part and operatively connected to said cutter-head for driving the same.

3. Apparatus of claim 2 wherein the means for driving the cutterhead comprises hydraulic motor means carried by said second ladder part.

4. Apparatus of claim 2 including a centrifugal pump carried by said second ladder part, a suction pipe extending from said cutterhead to the inlet of said pump and flexible conduit means connected to the outlet of said pump and connected to a second pump carried by said barge.

5. Apparatus of claim 4 wherein said flexible conduit means includes a pipe section carried by said link, a first swivel coupling connecting the outlet of said pump to one end of said pipe section, a pipe carried by said first ladder part and adapted to be connected at one end to said second centrifugal pump on said hull and a second swivel coupling connecting the opposite end of the pipe section carried by said link to an adjacent end of the pipe carried by said first ladder part.

6. Apparatus of claim 5 wherein said link is connected to said ladder parts by pairs of upper and lower laterally spaced bearing pins, fluid passages extending co-axially through the upper and lower'bearing pins on the side of said link adjacent the ends of said pipe section, said ends being connected through said swivel couplings and the passages in said pins to the outlet of said pump and to the pipe carried by said first ladder part, respectively.

7. Apparatus of claim 1 including support means connected to said second ladder part for exerting a lifting force thereon, and means responsive to changes in load on the support means by the second ladder part as the dredge pitches in seas for varying the lifting force of the support means so that the force exerted by the cutterhead on the bottom is at all times substantially constant.

8. Apparatus of claim 7 including manually operable control means carried on the hull for selecting the degree of lift exerted by said support means.

9. Apparatus of claim 7 wherein the support means comprises a hydraulic piston and cylinder connected between first and second ladder parts, an hydraulic inlet connected to said cylinder so as to deliver hydraulic pressure fluid to said piston in opposition to the weight of said second ladder part, conduit means connecting said inlet to the hydraulic cavity of an accumulator carried by said barge, and second conduit means including a manually adjustable pressure regulating valve connecting the pneumatic cavity of said accumulator to a source of pneumatic pressure. 

1. Dredging apparatus for use in heavy seas comprising a barge and an articulated ladder, said ladder comprising a first rigid upper ladder part having its inner end pivoted to said barge, a second rigid lower ladder part carrying adjacent its outer end a cutter-head, a downwardly extending rigid link having its upper end freely pivoted to the outer end of said first ladder part so that said link swingably depends from said outer end, said link having its lower end freely pivoted to the inner end of the second ladder part so that said second ladder part is angularly movable relative to the upper ladder part, and means for adjustably positioning said first ladder part at a selected angle relative to said barge so that the lower end of said link is positioned clear above the sea bottom during dredging operations in heavy seas.
 2. Apparatus of claim 1 including means carried by said second ladder part and operatively connected to said cutter-head for driving the same.
 3. Apparatus of claim 2 wherein the means for driving the cutterhead comprises hydraulic motor means carried by said second ladder part.
 4. Apparatus of claim 2 including a centrifugal pump carried by said second ladder part, a suction pipe extending from said cutterhead to the inlet of said pump and flexible conduit means connected to the outlet of said pump and connected to a second pump carried by said barge.
 5. Apparatus of claim 4 wherein said flexible conduit means includes a pipe section carried by said link, a first swivel coupling connecting the outlet of said pump to one end of said pipe section, a pipe carried by said first ladder part and adapted to be connected at one end to said second centrifugal pump on said hull and a second swivel coupling connecting the opposite end of the pipe section carried by said link to an adjacent end of the pipe carried by said first ladder part.
 6. Apparatus of claim 5 wherein said link is connected to said ladder parts by pairs of upper and lower laterally spaced bearing pins, fluid passages extending co-axially through the upper and lower bearing pins on the side of said link adjacent the ends of said pipe section, said ends being connected through said swivel couplings and the passages in said pins to the outlet of said pump and to the pipe carried by said first ladder part, respectively.
 7. Apparatus of claim 1 including support means connected to said second ladder part for exerting a lifting force thereon, and means responsive to changes in load on the support means by the second ladder part as the dredge pitches in seas for varying the lifting force of the support means so that the force exerted by the cutterhead on the bottom is at all times substantially constant.
 8. Apparatus of claim 7 including manually operable control means carried on the hull for selecting the degree of lift exerted by said support means.
 9. Apparatus of claim 7 wherein the support means comprises a hydraulic piston and cylinder connected between first and second ladder parts, an hydraulic inlet connected to said cylinder so as to deliver hydraulic pressure fluid to said piston in opposition to the weight of said second ladder part, conduit means connecting said inlet to the hydraulic cavity of an accumulator carried by said barge, and second conduit means including a manually adjustable pressure regulating valve connecting the pneumatic cavity of said accumulator to a source of pneumatic pressure. 